Ruch U.S. Pat. No. 1,943,931 describes a test strip that is placed between the jaws of a fixture. The faces of these jaws have serrations, file marks, or the like.
Dillon U.S. Pat. No. 2,419,711 describes a gripping device that is similar to that of the Ruch patent. This patent discloses serrated gripping faces.
DeNicola U.S. Pat. No. 3,224,259 also describes a gripping device that is similar to that of the Ruch patent. The gripping surfaces of the device shown in the DeNicola patent have teeth.